Surprising New Images of Pōwehi Black Hole Unveiled
Credit: EHT Collaboration
On September 16th, Event Horizon Telescope researchers published a paper in the Astronomy & Astrophysics journal unveiling new photos of Pōwehi taken in 2021. Pōwehi is a supermassive black hole at the center of the M87 galaxy, first imaged by the EHT in 2017. Seeing the progression of images from 2017 to 2021 helps us better understand how matter and energy behave in the space that surrounds black holes.
The Event Horizon Telescope (EHT) is a collaborative international research project that links telescopes across the world to image black holes, including two on Maunakea. Located on Maunakea, the James Clerk Maxwell Telescope (JCMT) plays an integral role for EHT as the largest single-dish, submillimeter telescope in the world. JCMT helped take the very first measurements of Pōwehi, laying the foundation for the creation of the EHT.
“Our participation brings really great visibility to the world of what we’re doing here,” said Geoffrey Bower, Director of the JCMT. “It’s inspiring for our staff members and everyone involved to be a part of something bigger. I think people take a lot of pride in the fact that Maunakea has contributed to this.”
Pōwehi Polarization Patterns Reverse
In 2017, the EHT took the first-ever image of a black hole. Larry Kimura, associate professor of Hawaiian language and studies at the University of Hawaiʻi at Hilo, gave it the name Pōwehi. The name, sourced from the Kumulipo, combines Pō - the powerful, creative darkness - and wehi - the adornment that would crown ali’i, for the bright orange ring crowning the black hole, as described in this 2019 UH Hilo article.
The Maunakea telescopes helped produce this image, which revealed a ring of polarization surrounding the Pōwehi supermassive black hole. The orange ring around the black hole in the images is hot, glowing plasma, and light waves - the thin stripes in the image - have a preferred direction to spiral around the black hole, based on magnetic fields. Now, combined with images taken in 2018 and 2021, they show that the magnetic field direction of the ring has completely flipped.
Credit: EHT Collaboration, Amy C. Oliver/CfA
The polarization ring shows strong magnetic fields around the black hole, which are involved in channeling the flow of matter into the black hole. When looking at all three images, researchers saw that these magnetic fields appeared to spiral in one direction before settling in 2018, and then reversing direction in 2021.
Importantly, the ring has not changed in size or shape over the course of these images, which confirms Einstein’s theory of general relativity. However, the light in the ring is asymmetric, and the location of that asymmetry is changing over time. That tells us that the flow of matter into the black hole is turbulent, rather than a steady stream of material being consumed.
This confirms that the environments around black holes are extremely dynamic and opens up many new questions about how matter and energy behave near black holes.
Scientists also found the first evidence for a connection between the ring, or accretion disc, and the superpowerful “jet” near the base of Pōwehi. They were able to detect emissions from the jet coming out of Pōwehi for the first time, revealing a powerful beam of radiation and energetic particles traveling at nearly the speed of light.
Jets like Pōwehi’s are crucial in regulating the formation of stars and distributing energy across wide swaths of space. Bower explained, “It determines how stars are formed in galaxies, how galaxies grow over time, and how galaxies in clusters interact with each other.”
Constant Improvements
Prior to and during the 2021 campaign, the Hawaiʻi telescopes were the western edge of the EHT, but last year, the EHT added a telescope in Korea. “Hawaiʻi has moved from being the edge to being in the center of the array for an extended amount of time,” said Bower.
Two new telescopes in Arizona and France also contributed to the 2021 images. “It’s great to have new telescopes joining in on this exciting adventure of black hole imaging,” said Bower. “It’s a sign of how important this science is that a global effort is underway to image Pōwehi. We plan to do this science for many years to come.”
Upgrades to the instruments at the JCMT also helped make these new images possible, including a brand new radio wave receiver, which they used for the first time in 2021. The new receiver is extremely sensitive, and researchers saw significant improvements in data quality compared to the previous instrument.
A Bright Future for Maunakea Telescopes
In the future, JCMT hopes to turn this new receiver from detecting a single wavelength to multiple at once. “It’ll be like going from black and white to color TV”, Bower described. “It’ll triple the amount of data we’ll be able to collect, and we’ll be able to make much more beautiful images.”
“It’s been a long time coming to get this multiyear view of Pōwehi,” Bower said, “and this demonstration that it changes over time gives us confidence.”
In the spring of 2026, JCMT and the other EHT collaborators plan to take the first-ever black hole “video” by imaging Pōwehi twice a week over the course of a few months. In comparison, their previous imaging of Pōwehi has been about once per year. “We really don’t know whether most of the changes happen on a short time scale. It could be cyclical changes,” said Bower. “There’s a whole range of things we’d like to see.”
With upcoming projects like this, Pōwehi’s time in the spotlight is far from over. Bower elaborated, “The whole experience of working with Larry [Kimura] and then sharing the name with the community here in Hawaiʻi has been such a rich reward for all of us who’ve been involved. It has certainly deepened my knowledge and understanding of Hawaiian history and Hawaiian culture, and I think it’s brought that knowledge to the world.”
